Cache Valley Idaho PM2.5 Nonattainment Area SIP

47

section 5.1.1 and depicted in Figure 24, SO2 from transportation on the Idaho side of the 

CVNAA is not significantly contributing to nonattainment. Therefore, Idaho is making the 

determination to not include SO2 emissions in the MVEB. Idaho will include NOx, VOC, and 

reentrained road dust in the MVEB.

The Utah side of the CVNAA will continue to use the Cache Valley MPO for future conformity 

determinations. Since the Idaho side of the CVNAA does not have an established MPO, the 

entire Franklin County will be considered a rural donut area for conformity purposes. Rural 

donut areas are geographic areas outside a metropolitan planning area boundary but inside the 

boundary of a nonattainment or maintenance area that contains any part of a metropolitan area as 

described in 40 CFR 93.101.

5.5.2 Motor Vehicle Emission Budget

The MVEB is comprised of on-road mobile sources including fugitive dust from paved and 

unpaved roads and vehicle emissions (exhaust, tire, and brake wear). EPA’s MOVES model was 

used to develop vehicle emissions estimates for the MVEB. The MVEB becomes applicable 

when the EPA determines that the budget is adequate for transportation conformity purposes. In 

accordance with the conformity rule, the emissions budget acts as a ceiling on emissions in the 

year for which it is defined or until a SIP revision modifies the budget. 

The MVEB is developed as part of the SIP to place a ceiling or cap on emissions from 

transportation projects. The conformity process compares projected emissions from the TIPs and 

LRTPs with the budgeted emissions set out in the SIP MVEB. The emissions budgets included 

as part of this SIP are shown in Table 9. The conformity rule will require the emission 

projections from future TIPs and LRTPs be less than or equal to the budget levels. The 

conformity process ensures that transportation projects will not cause or contribute to NAAQS 

violations.

Table 9. Motor vehicle emission budget for the Idaho side of the Cache Valley nonattainment area.

Year County NOx (ton/day) VOC (ton/day)

Total PM2.5

(ton/day)

2008 Franklin 0.879 0.612 0.496

2014 Franklin 0.501 0.386 0.429

2019 Franklin 0.360 0.263 0.429

Notes: nitrogen oxides (NOx); volatile organic compounds (VOC); particulate matter 2.5 (PM2.5)

5.5.3 Adequacy Determination

Before the MVEB can be used for conformity purposes, it must demonstrate adequacy. For EPA 

to determine the MVEB is adequate, the conformity rule requires that MVEB emissions must be 

considered with all other emissions sources and be consistent with the applicable SIP. Modeling 

must demonstrate that all emission sources combined (point, area, and mobile sources) will not 

cause or contribute to a violation of the PM2.5 NAAQS. As discussed above, a modeling 

demonstration was performed by UDAQ that included point, area, and mobile sources from both 
Cache Valley Idaho PM2.5 Nonattainment Area SIP

48

Idaho and Utah, showing attainment and maintenance of the NAAQS by 2014. This information 

is available in Appendix B.

6 Administrative Requirements

Table 10 provides a crosswalk between the regulatory requirements in 40 CFR 51 this SIP must 

address and how Idaho has met the requirements.

Table 10. Crosswalk between the regulatory requirements and how the requirement is met within 

this State Implementation Plan.

Regulatory Requirement (paraphrased) How Idaho Met Requirement

§ 51.102 Public hearings. States must provide notice, 

provide the opportunity to submit written comments, and 

allow the public the opportunity to request a public hearing.

Public participation in the development of 

this plan is discussed in section 6.2.

IDEQ will provide a 30-day public comment 

period with a public hearing. Complete 

documentation of the public comment 

process will be included with the submittal 

of this plan to EPA. 

§ 51.103 Submission of plans, preliminary review of plans. Idaho will submit plan in accordance to 

letter from Region 10 dated April 26, 2011.

§ 51.110 Attainment and maintenance of national 

standards. Each plan providing for the attainment of a 

primary or secondary standard must specify the projected 

attainment date.

Idaho’s 2006 PM2.5 Infrastructure SIP was 

submitted to EPA June 25, 2010, and 

updated August 8, 2011. 

The attainment date is January 1, 2015 

§ 51.111 Description of control measures.

Each plan must set forth an enforceable control strategy.

The control strategy for Franklin County is 

discussed in section 5.

In addition, the State of Utah has submitted 

a plan to EPA Region 8 that contains 

enforceable control measures for Cache 

County.

§ 51.112 Demonstration of adequacy. Each plan must 

demonstrate that the measures, rules, and regulations 

contained in it are adequate to provide for the timely 

attainment and maintenance of the national standard that it 

implements.

The adequacy of control measures for 

Franklin County is discussed in sections 4 

and 5.

In addition, the State of Utah has submitted 

a plan to EPA Region 8 demonstrating the 

adequacy of control measures for Cache 

County.